Plant materials are an economic source of a number widely utilized functional food ingredients, notably biopolymers. Thus, it is well-known in the art to isolate functional food ingredients such as starch, inulin, pectin and proteins, from plant materials.
In addition, there is an increasing interest for plant-derived functional food ingredients that can be used as natural or ‘friendly label’ alternatives for existing ingredients that consumers perceive as less desirable. These functional ingredients include plant-derived flavour components, taste enhancers, salt replacers, anti-oxidants, emulsifiers and colourings.
WO 2004/041003 discloses an edible flavor improver comprising an essentially non-volatile mixture containing non-sucrose components of sugar beet extract, said mixture being effective in enhancing the organoleptic characteristic(s) of ingestible products and being obtainable by fractionation of said sugar beet extract. Example 3 describes a fraction that is obtained from beet molasse. The main cations of the sample were Na and K (about 100 g/kg of liquid of each). The sample contained about 5.5% rafinose, about 1.7% sucrose, and less than 0.1% of each of glucose, fructose, inositol and betaine. The sample contained 12.3% lactic acid, 6.1% L-2-pyrrolidone-5-carboxylic acid (PCA), 2.8% acetic acid, 1.9% formic acid and 1.0% citric acid, 0.23 aspartic acid, 0.2% glutamic acid and minor amounts of neutral amino acids. These percentages are calculated on the total dry substance in the fraction.
In order to produce plant-derived functional food ingredients in high yield and/or high purity, it is often necessary to make use of sophisticated separation techniques, such as chromatographic techniques.
WO 2009/080763, for instance, describes a method for preparing an umami active fraction from concentrated tomato serum (12.5° Brix) comprising the following steps:                subjecting the concentrated tomato serum to ultrafiltration to yield a permeate that is substantially free from lycopene;        concentrating the permeate to 40° Brix strength;        fractionating the concentrated permeate using ion exclusion chromatography;        collecting a fraction of the eluate (0.43-0.66 bed volume) that is enriched in glutamic acid;        concentrating the eluate fraction to 20° Brix;        fractionating concentrated eluate fraction using ion exclusion chromatography and using the same conditions as in the first fractionation step.        collecting a fraction of the eluate (0.43-0.66 bed volume) that is further enriched in glutamic acid.        
WO 2010/069743 describes a similar method for preparing an umami enhancing composition from concentrated tomato serum. WO 2009/080768 describes a similar method for preparing a natural sweetening agent from concentrated tomato serum, also using ion exclusion chromatography.
A drawback of the use of ion exclusion chromatography in the aforementioned methods resides in the fact that the separation efficiency of the ion exclusion resins was found to decline rather rapidly over time, making it necessary to regenerate the column material after short intervals.